Chronic kidney disease (CKD) patients have high cardiovascular mortality and morbidity. The presence of traditional and CKD related risk factors results in exaggerated vascular calcification in these patients. Vascular calcification is associated with reduced large arterial compliance and thus impaired baroreflex sensitivity (BRS) resulting in augmented blood pressure (BP) variability and hampered BP regulation. Baroreflex plays a vital role in short term regulation of BP. This review discusses the normal baroreflex physiology, methods to assess baroreflex function, its determinants along with the prognostic significance of assessing BRS in CKD patients, available literature on BRS in CKD patients and the probable patho-physiology of baroreflex dysfunction in CKD.
Didactic lecture is an effective method to quickly pass on a high volume of information to a large number of students. However, if not well designed, lectures can be monotonous and provide only passive learning, with little scope for higher order learning skills. To address this drawback of lectures, we supplemented it with case-based learning (CBL), which has been shown to promote self-learning. After giving an overview of gastrointestinal physiology through lectures, CBL on peptic ulcer disease was implemented for first-year Bachelor of Medicine, Bachelor of Surgery students. The present study aimed to evaluate the students’ and teachers’ opinions on the notion of supplementing lectures with CBL. In previous reports, discussion using clinical cases was primarily employed as the solitary component for conducting CBL. In the present study, three different but mutually exclusive components, such as case discussion, concept map, and critical thinking exercise on a specific topic in gastrointestinal pathophysiology, were integrated to form the multicomponent CBL (MC-CBL). Students reported that MC-CBL could promote application of the knowledge learned in lectures in a more appropriate context (92.42% positive response), enhance their learning efficiency (98.46% positive response), promote their active participation in the learning process (98.48% positive response), and help them in integrating physiological concepts with clinical science (98.46% positive response). Teachers observed that MC-CBL could promote active learning, analytic, and problem-solving skills of students. In conclusion, MC-CBL appeared to be an effective supplement for the lectures, providing an opportunity for the students to relate the knowledge learned during lectures.
Background/Aims: Endogenous Cushing's syndrome is associated with a higher risk of cardiovascular morbidity and mortality. Previous literature suggested multiple possible links by which hypercortisolism may alter the autonomic control of cardiovascular functions. We investigated the impact of chronic endogenous hypercortisolism on the autonomic regulation of cardiac functions by short-term heart rate variability analysis. Methods: Eighteen patients with endogenous Cushing's syndrome and 20 age-, gender- and BMI-matched controls participated in the study. ECG signal was acquired in lead II configuration for 5 min and heart rate variability assessment was made in both time and frequency domain using the extracted RR interval data. Results: All time and frequency domain measures of heart rate variability were significantly (p < 0.05) lower in the patient group compared to the control group. The patient group had an altered sympathovagal balance with low frequency/high frequency band ratio significantly higher than the control group [1.857 (0.6747-2.610) vs. 0.8581 (0.4779-1.352); p = 0.0253]. A significant negative correlation was obtained between normalized high frequency power of heart rate variability and basal cortisol levels (r = -0.6594; p = 0.0029). Multiple linear regression analysis identified age, disease duration (in months), basal cortisol levels and systolic blood pressure as independent predictors of normalized high frequency power. Conclusion: Findings of the study clearly portrayed the diminished autonomic modulation of heart rate in endogenous Cushing's syndrome and its possible relationship with hypercortisolism as the main causative factor. Diminished heart rate variability may be an indicator of the increased risk of cardiac mortality in these patients.
Autonomic dysfunction is an independent predictor of cardiovascular and all-cause mortality after myocardial infarction (MI). We tested the effects of a 12-week yoga-based cardiac rehabilitation program on heart rate variability (HRV) in 80 patients post-MI. This randomized controlled trial with two parallel groups was carried out in a tertiary care institution in India. The yoga group received 13 hospital-based structured yoga sessions as an adjunct to standard care. Control group participants received enhanced standard care involving three brief educational sessions with a leaflet on the importance of diet and physical activity. HRV was measured in all participants with lead II electrocardiogram (ECG) signals. One yoga group patient's data were excluded due to ECG abnormalities. Baseline measurement was done 3 weeks post-MI, and postintervention assessment took place at the 13th week. HRV frequency and time domain indices were analyzed. There were no significant between-group differences in the HRV time domain indices. Frequency domain indices showed significant between-group differences in HF power (absolute) (yoga vs. control: 114.42 [−794.80–7,993.78] vs. −38.14 [−4,843.50–1,617.87], p = 0.005) and total power (nu) (yoga vs. control: 44.96 [21.94] vs. −19.55 [15.42], p = 0.01) with higher HF power and total power (nu) in the yoga group. It should be noted that these results cannot be generalized to high risk patients. Respiratory frequency control to check for influence of respiratory rate on RR interval was not evaluated. This short-term yoga-based cardiac rehabilitation program had additive effects in shifting sympathovagal balance toward parasympathetic predominance while increasing overall HRV in optimally medicated post-MI patients.
Insulin resistance is associated with endothelial dysfunction in type 2 diabetes mellitus, which can lead to impaired vascular reactivities of both systemic and cerebral circulations. Appropriate 'correction' of vascular reactivity results for non-endothelium-dependent systemic effects avoids misinterpretation of endothelial function. Therefore, we 'corrected' vascular reactivity results and explored the potential correlations between systemic vascular reactivity, cerebrovascular reactivity and insulin resistance. In 34 patients, 'systemic vascular reactivity' was assessed by quantifying reactive hyperaemia. Cerebrovascular reactivity was assessed by quantifying changes in cerebral blood flow velocity during hypercapnia. To minimize the influence of non-endothelium-dependent systemic effects on vascular reactivity results, 'corrected systemic vascular reactivity' was calculated by normalizing systemic vascular reactivity using the measurements from the contralateral side; and cerebrovascular reactivity results were corrected by calculating percentage and absolute changes in cerebrovascular conductance index ('percent cerebrovascular conductance index' and 'delta cerebrovascular conductance index', respectively). Insulin resistance was estimated by homeostatic model assessment. Correlation between conventional cerebrovascular reactivity and systemic vascular reactivity was not significant. But correlations between 'corrected systemic vascular reactivity' and 'percent cerebrovascular conductance index' (r = 0.51; p = 0.002) and 'corrected systemic vascular reactivity' and 'delta cerebrovascular conductance index' (r = 0.50; p = 0.003) were significant. Among all vascular reactivity parameters, only 'delta cerebrovascular conductance index' was significantly correlated with homeostatic model assessment of insulin resistance (r = −0.38; p = 0.029). In conclusion, endothelial function in the systemic and cerebral circulations is moderately correlated, provided that vascular reactivity estimates are corrected for non-endothelium-dependent influences.
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